Grinding machine



Aug. 6, 1957 H. 1.. BLOOD ETAL 2,301,502

' GRINDING MACHINE Filed July 16, 1956 4 Sheets-Sheet l Harold L. Blood William 11/. Ufa/re Aug. 6, 1957 BLOOD ETAL 2,801,502

GRINDING MACHINE Filed July 16, 1956 4 SheetsSheet 5 u aw INVENTORS Harold LBZoocZ Ufilliam 21/. Zl/a're F1 -0 neg United States Patent '6 GRINDING MACHINE Harold L. Blood, Worcester, and William- W. Ware, Holden, Mass, assignors to The Heaid Machine Company, Worcester, Mass, a corporation of Delaware Application July 16, 1956, Serial No. 598,179

11 Claims. (Cl. 51-16S) This invention relates to a grinding machine and more particularly to apparatus for abrading a surface of revolution with a high degree of accuracy.

It is conventional practice in the art of grinding, particularly when the surface to be abraded is an internal bore or the like, to provide for the rotation of the workpiece about its axis and for movement laterally of its axis while a rotating Wheel reciprocates axially within the bore. Furthermore, it has been Well-known to regulate the amount of material removed by terminating the grinding cycle in response to measurements of bore diameter taken by a gage which enters the bore from the end opposite the wheelhead, it being standard practice to cause the wheel at every reciprocation to move out of a portion of the bore at the gage end and to cause the gage to enter at that time. This practice has several limitations which render it less than perfect when extreme accuracy is desirable. To begin with, the wheel must be removed from a considerable portion of the bore to permit the gage to enter, particularly when grinding bores of short length and small diameter. Since the gage is to enter the bore at each reciprocation of the wheel, the wheel must be shorter than the bore and must make long strokes. Now, a short wheel and a long stroke are undesirable because, when thewheel is removed froma portion of the Work surface, that portion will remain relatively high. Upon returning to this portion of the surface, the wheel must remove material at a faster rate than in the other portions of the surfaceyhigher production would be obtainable if all parts of the surface could be ground at this high rate but, since there is an upper limit in a given situation to the rate of material removal, a substantial portion of the grinding cycle is relegated to less than the fastest rate. It would, therefore, be decidedly advantageous to be able not only to use a Wheel that is longer than the bore, but also to be able to use it with a short stroke without the necessity of removing it from a portion of the bore during each reciprocation in order that the gage enter. Another diificulty experienced with such apparatus is that the gage resides in the bore for a very short length of time and this leads to inaccuracy of gaging since it is too short a period for fluctuations in the gaging apparatus to smooth out. lengthening of this period for more accurate gaging causes the high spot to be even higher. Also, merely permitting the gage to enter one end of the bore emphasizes inaccuracies due to taper; if gaging takes place midway between the ends of the bore, the error due to taper is reduced by half. Furthermore, it has been necessary with prior art machines of the type described above to separate the wheel from the work at a fixed part of the stroke, thus leaving a high spot in every case; the reciprocations were made very rapid to minimize the amount of stock removed per stroke, but, even .so the accuracy of the machine could be no greater than this amount. These and other deficiencies of the previouslyknown apparatus have been obviated by the present in- .Yfintioninanovelmanner.,..

Any ,7 i

bore during the grinding cycle.

Another object of the invention is the provision of an internal grinding machine in which the machine gage remains in the bore for a length of time sufficient to permit accurate gaging. I

A still further object of the instant invention is the provision of an internal grinding machine in which the machine gage may reside midway between the ends of the bore during gaging.

Another object of this invention is the provision of an internal grinding machine in which thewheel may reciprocate slowly within the bore without loss of accuracy due to a'high portion where gaging takes place.

It is a further object of the invention to provide an internal grinding machine in which the reciprocating wheel may be removed from the work at any point in its stroke.

lt is-another object of this invention to provide an internal grinding machine having means to compensate for variations which may take place in the machine gage due to thermal effects and the like.

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, the mode of its operation and the manner of its organization may be better understood by referring to the following description taken in connection with the accompanying drawings forming a part thereof, in which:

Figure l is a somewhat schematic front elevational view of an internal grinding machine embodying the principles of the present invention,

Figure 2 is an enlarged view of a portion of the apparatus shown in Figure 1,

Figure 3 is a schematic view of electrical and pneumatic apparatus associated with the apparatus,

Figure 4 is a sectional view of the apparatus taken on the line IV-IV of Figurel, and

Figure 5 is a schematic view of a modified version of the invention.

In this specification, the expression transverse? will be used to indicate a direction at a right angle to the axis of rotation of the workpiece, While the expression longitudina will be used to indicate a directionparallel to that axis. 1

Referring first to Figure 1, wherein is best shown the general features of the invention, the internal grinding machine, designated generally by the reference numeral 10, is shown as comprising a base 11,Wlth Which are associated 'a wheelhead 12, a workhead13 and a truing device 14. From the Wheelhead 12 extends an abrading tool such as a cylindrical wheel 15. From the workhead 13 extends a chucking means such as a magnetic platen 16 driven through a pulley 17; a workpiece 18 is held and rotated by the platen and supported by a supporting member 19. Extending through and slidably supported by the workhead is a shaft 21 havingagaging head 22; the head resides in a recess in the platen 16. A coil spring 23 surrounds the shaft 21 and lies under compression between the head 22 and the back wall of the platen. As is evident in Figure 2, the gaging head 22 is provided with a cylindrical surface on which fine air passages 24 open, these passages extending radially inwardly and connected to a passage 25 which extends axially through the shaft 21 and terminates in a flexible conduit 26, The end of the shaft opposite the gage head is provided with a collar 27 the inner side of whichycontacts the endof one leg of a bell crank 28 which is pivotally attached to anabutment 29 extending from the workhea'd"13; A

Patented Aug. 6, 1957 finger 31 extends upwardly from the said one leg; the end of this finger lies in a notch 32 formed in the plunger of a valve 33 extending from the worlthead. On the end of the other leg of the bell crank 28 is mounted a roller 34 which is located to engage a cam 35 extending up wardly from one end of a table 36 which is elongated longitudinally of the apparatus. The wheelhead 12 is fastened to the other end of the table and the table is mounted for longitudinal sliding movement on the base 11. The cam 35 is formed with a level high portion 37 on which the roller 34 rests when the table is located in position to allow the Wheel to reside in the bore of the workpiece.

Extending downwardly from the table 36 is a dog 39 adapted on occasion to engage a switch 41; a dog 42 having a pivoted latch 38 is also mounted on the table for engagement with a lever 43 which engages and activates the plunger of a reversing valve 44. An actuating finger 45 is mounted on the base for vertical sliding to contact and'move the dog 42; a solenoid 46 is mounted on the base in a position such that its plunger may contact and raise the finger 45, thus lifting the dog latch 38 and allowing it to run past the lever 43. Another dog extends downwardly from the table.

Theiworkhead 13 is dovetailed to a conventional bridge 47 which straddles the table 36 permitting transverse feed motion of the workhead. A conventional feed screw 48 is mounted in the bridge and engages a nut Stl fastenet to the workhead 13 for bringing about the feed motion.

Mounted on the screw 48 is a cam wheel 49 which rotates with the screw 48. The screw and cam wheel are rotated clockwise by a conventional feed box 60, including a reversing valve, actuating cylinder, rack and pinion, as shown in Figure 3, to rotate the feed screw 48 and to feed the workpiece into the wheel. from the outer periphery of the wheel is a dog 51 adapted on occasion to engage a switch 52 fixedly mounted on the feed box 60 with its actuating finger in the path of the dog as the wheel rotates. At the other side of'the wheel, a cam 53 is mounted to extend outwardly with its formed surface adjacent a pneumatic nozzle 54 fixed to the feed box 60. Attached to the nozzle is a flexible conduit 55.

Figure 3 shows schematically the arrangement of a portion of the electrical and pneumatic circuits in the apparatus. Electrical power lines 56 and 57 are connected to a source of power, not shown. The switch 41, as is evident, consists of two sets of isolated contacts, each sethaving its own contactor. One set of contacts 'is connected on one side to the power line 56 and on the other'side through the coil 58 of a relay 59 to the other power line 57. The relay 59 has four sets of contactors 61, 62, 63 and 64. The contactors 62 and 64 are normally closed, While contactors 61 and 63 are normally open; when the coil 58 is energized, however, the contactors 62 and 64 are opened and the contactors 61 and 63 are closed. The contactor 61 is connected on one side to a point between the coil 58 and the contactor portion of the switch 41 connecting it to the line 56 and on the other side the contactor 61 is connected to one side of the other contactor portion of the switch 41; this contactor portion is, in turn, connected on its other side to the line 57 through the coil 65 of a solenoid 66. The plunger of the solenoid is arranged to contact and actuate the plunger of a valve 67. The valve is constructed to be spring-biased to closed position,'but, when the coil 65 is energized, the valve is actuated to open position to connect a conduit 68 to one end of the conduit 26 the other end of which is connected to the gage shaft 21, as is evident in Figure 1. Tu'rningag'ain to the relay 59, it can be seen that the contactor 62 is connected on one side to the line 57 through the. coil of the solenoid 46; the other side is connected to the line 56through one contactor portion of thes'witch52 which has two contactor'portions, One side Extending of the contactor 63 is connected to the side of the contactor 61 which is connected through the switch 41 to the coil the other side of the contactor 63 is connected to the side of the contactor 62 which is connected to the switch 52, as is one side of the contactor 64. The other side of the contactor 64 is connected through one contactor section of a double switch 69 to the line 56. The other contactor section of the switch 69 is connected on one side to the line 56 and on the other side through the coil of a solenoid 71 to the line 57; this other side is also connected through a switch 72 and the coil of a solenoid 73 to the power line 57. The switch 72 is a double-throw switch in which one contactor is connected to the switch 69, as has been stated, and the other is connected to the contactor of the double switch 52 which is not connected to the relay 59. Regarding the pneumatic circuit, a pressure regulating valve '74 is connected on its input side to a source of air under pressure, not shown. The output side of the valve is connected to conduit 75 which is attached to one side of a fixed restriction such as the orifice member 76; the other side of the orifice member is connected through a conduit 77 to the conduit 26 adjacent to its connection to the valve 67. The output side of the pressure regulating valve 74 isconnected by a conduit 73 to one side of a variable rest-rictor such as adjustable orifice member 79, the other side of which is connected to the conduit 55 which, as is evident in Figure 1, is connected to the nozzle 54. The member 79 is provided with a movable element 31 whose movement varies the size of the passage through the member. The element is moved longitudinally, as is indicated schematically, by the rotation of a ratchet wheel 82. This rotation is brought about by the action of pawls 83 and 84 which, in turn are actuated by solenoids 85 and 86, respectively. These solenoids are under the control of an after gage 87 of the type which includes an air gage which serves, when the workpiece varies from a predetermined range of values, to act through pressure switches to energize one of the solenoids 85 and 86. The conduit 55 is connected to a chamber 91 of a pneumatic actuator 88 having a diaphragm 89 which divides the actuator into two chambers 91 and 92; the other chamber 92 is connected by the conduit 68 to the valve 67. An actuating stem 93 connects the diaphragm 89 to the switch 69 and causes it to close when the pneumatic pressure in chamber 91 exceeds that in chamber 92. Connected to the conduit 68 between the valve 67 and the actuator 88 is a memory device such as a pressure reservoir 94.

Figure 4 shows some of the details of the truing device 14. The construction is similar to that shown and described in the patent application of Almon F. Townsend, Serial Number 473,650, filed December 7, 1954. Means is provided for turning and advancing a diamond 95 with every truing operation and for lifting the diamond away from the wheel after each truing operation. The diamond is mounted on a head 96 which is pivotally connected to an upward extension 97 of the base 11 by means of a longitudinal shaft 98. The solenoid 73 is mounted on the extension 97 and its plunger is connected to one end of a latch 99 the other end of which is hinged to the extension 97 of the base 11; a downwarddirected notch 10]. is provided in the intermediate portion of the latch 99. A bell crank 102 is pivotally connected to the base 11. One leg of the bell crank 102 is provided at its outer end with a. roller 103 adapted to engage a cam 104 extending upwardly from the table 36. The end of the other leg of the bell crank 102 is hingedly connected to the upper part of the diamond head 96; a pin 105 extends from the intermediate portion of this last-named leg in a position underlying the latch 99. A spring 106 maintains the latch 99 in a downwardly-biased condition. The diamond 95 is mounted on a shaft 107 which is threadedly mounted in the head 96. This shaft 75 may be turned and advanced by.manual actuation of knob 108 which acts on the shaft through bevel gears 109 and 111. This same movement of the shaft takes place when the diamond head is lowered because a pin 112 strikes the base 11 and moves upwardly into the head 96; the upward movement of the pin 112 causes a pawl 113 to act on a ratchet wheel 114 keyed to the shaft 107.

It will be understood that the machine will be provided with mechanisms and controls for causing it to perform a grinding cycle which are not shown and described in this specification but Which are related to the present invention and associated therewith. For the purpose of this application it may be assumed that the machine is constructed with the type of control apparatus shown and described in the patent of Schmidt et al., No. 2,771; 714, dated November 27, 1956. For instance, the solenoid 71, when energized, acts through a retraction valve and associated mechanism to cause the feed screw 48 to turn counterclockwise and retract the wheel from the bore. The valve 33 lies in the hydraulic circuit causing the cross-feed to take place when the plunger is in the left position shown in Figure 1.

The operation of the apparatus will now be readily understood in view of the above description. In Figure 1, the apparatus is shown as it exists when the table 36 is at the right hand end of its grinding stroke and has carried the wheel 15 to the position shown. Since the gage does not enter the bore during every stroke, it has been possibleto use a wheel which is considerably larger than the bore. The stroke selected is very short so that at no time during grinding does one end of the wheel enter the bore, so that never is a portion of the bore surface uncovered while the rest of the bore is being ground. The cross-feed screw 48, turning clockwise, turns the wheel 49 and carries the cam 51 to a position in which it strikes and closes the switch 52; this takes place at a pre-selected feed position. The closing of the switch 52 completes a circuit through the solenoid 46 by way of the 'normally'closed contacts 62 of the relay 59. The solenoid 4-6 raises the finger 45 which lifts the movable dog 42 over the lever 4 3 of the reversing valve 44. This causes the table 36 to continue to the right on an extended stroke until reversed by the dog 40. The table cam 35 is carried toward the right, allowing the roll 34 on the bell crank 28 to roll from the high portion 37 to the low portion. This permits the spring 23 to move the shaft 21 and the gage head 22 to the right, so that the head lies in the bore in the workpiece as shown in Figure2 and operates to gage the bore pneumatically after the valve 67 is opened. It also permits the valve 33 to be closed, stopping the cross-feed. Further movement of the table 36 causes the dog 39 to engage and close the switch '41, thus energizing the coil 58 of the relay 59. This closes the circuit through switch 52, contactors 63 of relay 59, switch 41 and the coil 65 of the solenoid 66. The solenoid opens the valve 67. Relay 59 is maintained in this condition by a holding circuit through contactors 63 and'61 until such time as the switch 52 opens.

The solenoid 66 maintainsthe'valve 67 in open position until the table switch 41 reopens. While the valve 67 is open the air pressure in the reservoir 94 and the pressure in chamber 92 of the actuator 88 is determined by-the leakage from the passages 24 in the gage head 22 and through the space between the head and the surface of the bore in the workpiece; that is to say, the reservoir is charged with a pressure which is a measure of the size of the bore at this point in the cycle. The reservoir retains this pressure during the subsequent portion of the grinding cycle and acts as a memory device.

. Eventually the finger 43 is struck by the dog 40 and the'table reverses its movement under the control of the reversing valve 44. Thetable returns to grinding position, opening the valve 33 and restartingthe crossfeed. The feed screw 48 turns clockwise carrying the cam wheel with it. As the cam 53 moves across the face of the nozzle54, the surface of the cam comes closer and closer to the nozzle, thus restricting the flow of air from the nozzle and gradually increasing the pressure in the conduit 55. This increase in pressure, in turn, makes itself felt in the chamber 91 of the actuator 88. Eventually, the pressure in the chamber 91 rises to the point when it exceeds that in the chamber 92; the stem 93 moves toward the switch 69 and closes it. A circuit is completed through the solenoid 71 and the solenoid, when thus energized, acts on a hydraulic retracting valve to reverse the direction of cross-feed. This separates the wheel 1:"; and the surface of the bore in the workpiece 18 in the transverse direction in the conventional manner, with the exception that this separation may take place at any point in the grinding stroke of the table. In the conventional machine, the work is separated from the workpiece surface at a fixed point in the stroke. When the switch 59 is closed, a circuit is also completed through the solenoid 46, thus causing the table to run to the right on an extended traverse for removal of the workpiece and its replacement by an unfinished workpiece.

If the switch 72 is in the lower position shown by the dotted line in Figure 3, the closure of switch 69 brings about the energization of the solenoid 73. Now, inthe normal, inoperative condition, the diamond head 96 is in a raised position and is held there by the fact that the pin 105 on the bell crank 102 lies in the notch 101 in the latch 99. The movement of the-plunger of the solenoid 73 lifts the latch 99, whereupon the bell crank 102 is permitted to move counterclockwise until the roller 103 rests on a low portion of the cam 104. At that time the diamond head 96 has been lowered and the diamond is in position to true the wheel 15. Also, the pin 112 has been pushed upwardly, causing the diamond to be advanced and turned. After the table 3 6 has carried the wheel past the diamond for truing, the roller 103 rides on the cam 104. The diamond head is rotated upwardly about the shaft 98 and the notch 101 is pulled down about'the pin by the action of the spring 106 on the latch 99. The wheel is, therefore, trued as the table runs out for loading.

If the switch 72 is in the upper position, indicated by the solid line in Figure 3, when the switch 52 is closed, the solenoid 713 will also be energized and truing will take place as the table andwheel run out for gaging. The final grinding is performed, therefore, by a freshly-trued wheel. This possible inaccuracy is compensated for by the provision of the after-gage 87. Each finished workpiece, as it is discharged from the working area, travels to the after-gage which is situated in a position far enough removed from the working area to be relatively free, of the thermal changes which occur in that area. Heating up of the machine gage head, for instance, causes it to expand and gage inaccurately. Expansion and contraction of large metal masses in the machine cause the distance between the diamond and the workhead centerline to vary and introduce inaccuracies. When the aftergage finds that the size of the finished workpiece is running off, it acts through the solenoids S5 and 86 and the pawls 83 and 84 to rotate the-ratchet wheel 82. This, in turn, advances or retracts the movable element 81 of the adjustable orifice member 79, depending on whether the workpieces are running oversize or undersize. If, for instance, the workpieces are running undersize, the aftergage advances the element 31, thus reducing the size of the orifice through which the air passes into the conduit 55. This means that at a given position of the surface of the cam 53 relative to the nozzle 54, the pressure in the conduit 55 and the chamber 91 of the actuator 88 will be lower. Therefore, the cross-feed will have to advance further before the pressure in chamber 91 ex ceeeds that in chamber 92 and the grinding cycle is ended by the closure of the switch 69 and energization of solenoid 46. Succeeding workpieces will, therefore, be larger than before the after-gage started correcting for undersize workpieces.

It can be seen, then, that, by the use of the present invention, wheel is in contact with all parts of the surface to be finished during the entire cycle, with the exception of the single stroke when machine gaging takes place. There is no high spot after each stroke to be ground down ata faster rate than the remainder of the bore, as is the case with previously-known machines of this type. The gage enters the bore and takes a measurement of the bore; a memory device controls the extent of the part of the grinding cycle subsequent to the gaging. The gage remains in the bore for suificient time so that an accurate measurement may be obtained; this is considerably better than attempting to gage in a few hundredths of a second, as is true with prior art apparatus. Furthermore, since the wheel moves on a greatly extended stroke away 'from the workhead, the gage may take its measurement near the midpoint between the ends of the bore, rather than near one end, so that any error in taper will be minimized; that is to say, if the bore were ground to the desired size at one end, the size at the other end would be greater or smaller than desired by the amount of the error in taper in the whole length. When the bore is gaged at its midpoint, the error in the diameter of either end due to error in taper is reduced by half. Also, the practice of the invention permits the wheel to be in continuous contact with the full length of the bore prior to separating the wheel from the work and permits separating them at any point in the stroke that the bore reaches the desired size. This makes for greater accuracy than when separation can occur only at a fixed point in the stroke, as is necessary in prior machines. With such prior machines it is necessary to use very rapid reciprocation to minimize the amount of metal removed per stroke, but, despite this precaution, the accuracy in sizing can be no better than this amount; with the present machine, the accuracy is not limited in this way and the rate of axial reciprocation of the wheel may be relatively slow.

In Figure is shown a variation of the invention in which a work head 113 has a plug gage 122 which advances to the bore of a workpiece 118 mounted on a platen 116 when the grinding wheel is removed. The gage is conical and advances further and further into the workpiece as the bore becomes larger. The outer end of the gage rod 125 is formed with a surface 153 which is inclined to the rod axis. A pneumatic nozzle 154 is fixed to the workhead and is directed toward this surface. A conduit 155 leads to a valve 167 and a conduit 178. The other end of the conduit 178 is connected to a source of air under pressure through a pressure-regulating valve 174 and a restriction 179 is interposed in the conduit 178. A valve 181 is connected on one side to the conduit 178 between the valve 174 and the restriction 179 and on the other side to a conduit 177 leading to the valve 167. The other side of the valve 181 is connected to a chamber 191 of a diaphragm-type switch 190. The switch comprises a housing divided into the chamber 191 and a chamber 192 by a diaphragm 189. A pin 193 is fastened to the center of the diaphragm and extends out of the housing in position to strike the normally-open switch 169. The chamber 192 is connected to the valve 167 by a conduit 168. The valve 167 is of the plunger type and is actuated by the plunger 166 of a solenoid 165 which is connected in series with a switch 141 from a power line 156 to a power line 157. The switch 169 is connected in series with a coil 146 between the same two power lines. The valve 167 is formed to connect the conduit 177 to exhaust when the solenoid is energized and, at the same time, to connect the conduits 155 and 168. At all other times the conduit 177 is blocked, as are the conduits 155 and 168 where they enter the valve. At a certain point in the feed, the switch 141 is closed, thus energizing the solenoid 165. At the same time the wheel is retracted for dressing and the gage enters the bore as far as it will go. The chamber 191 is reduced to atmospheric pressure through the conduit 177 and exhaust. The chamber 192, on the other hand, is suddenly subjected to the pressure in the conduit 155. Now, the pressure in the conduit is dependent on the amount of air escaping from the nozzle 154, which, in turn, depends on how far from the surface 153 the nozzle resides. The larger the bore in the workpiece, the farther the gage will extend into it, and the farther from the nozzle will be the surface 153. The pressure felt in the chamber 192 is, therefore, a measure of the size of the bore at the end of a fixed period of grinding. When the wheel has been dressed and returns to the workpiece, the switch 141 is opened and the plunger of the valve 167 slides to the left. The conduit 168 and the chamber 192 is now entirely closed and the pressure therein is representative of the measured size of the bore. The connection to exhaust through the conduit 177 of the chamber 191 is also cut off, so the pressure begins to build up at a rate determined by the valves 174 and 181, the restriction 179 and the nozzle 154. Eventually the pressure in the chamber 191 exceeds that in the chamber 192 and the switch 169 is closed to terminate the cycle. The period of time required to build the pressure .in chamber 191 to equal and exceed that in chamber 192 is longer when the pressure in chamher 192 is higher. Such a higher pressure indicates a small bore in the workpiece at the end of the first period. A longer second period of grinding will, therefore, result, so that the final bore will be of the desired diameter.

While certain novel features of the invention have been shown and described and are pointed out in the annexed claims, it will be understood that various omissions, substitutions, and changes in the forms and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention.

The invention having been thus described, what is claimed as new and desired to secure by Letters Patent is:

1.. An internal grinding machine comprising means for holding a workpiece for rotation thereof, an abrading tool for performing a finishing abrading operation cycle, a gage, means for rotating and feeding the tool transversely to bring about the said abrading operation, means causing the tool to reciprocate axially within the workpiece during a portion of the cycle, means for causing an interruption of the said abrading operation and causing the tool to be withdrawn axially from the workpiece and then to re-enter the workpiece, means causing the gage to enter the workpiece during the said interruption to obtain a signal indicative of the size of the bore, a memory device for receiving the signal from the gage and retaining it, and means responsive to the signal retained by the memory device to control the extent of the feed subsequent to the interruption and to retract the tool relatively from the work at any point in the reciprocating stroke.

2. An internal grinding machine comprising means for holding a workpiece for rotation thereof, a wheel having its axis parallel to the normal axis of the workpiece for performing a finishing abrading operation cycle, a gage, a first means for feeding the wheel laterally to bring about the said abrading operation, a second means for moving the wheel axially, the said second means causing the wheel to reciprocate axially Within the workpiece during a portion of the cycle, means associated with the first means for terminating the said reciprocations and causing the second means to withdraw the wheel axially from the workpiece for a period of time before resuming the said reciprocations, means causing the gage to enter the workpiece during .the said period to obtain a signal indicative of the size of the bore, a memory device for receiving the signal from the gage and retaining it, means for continuously comparing the signal to a standard signal "which standard signal increases in value as the cycle progresses, and means terminating the cycle when the gage signal and the standard signal reach a predetermined relationship.

3. An internal grinding machine comprising means for r a 9 a holding a workpiece for rotation thereof, a wheel having its axis parallel to the normal axis of the workpiece for performing a finishing abrading operation cycle, a pneumatic machine gage, a first means for feeding the wheel laterally to bring about the said abrading operation, a second means for moving the wheel axially, the said second means causing the wheel to reciprocate axially within the workpiece during a portion of the cycle, means associatedwith the first means for terminating the said reciprocations and causing the second means to withdraw the wheel axially from the workpiece for a period of time before resuming the said reciprocations, means causing the gage to enter the workpiece during the said period to obtain an air pressure signal indicative of the size of the bore, a reservoir for receiving the pressure signal from the gage and retaining it, means for continuously comparing the signal to a standard air pressure signal which standard signal increases in value as the cycle progresses, and means terminating the cycle when the gage signal and the standard signal reach a predetermined relationship.

4. An internal grinding machine comprising means for holding a workpiece for rotation thereof, a wheel having its axis parallel to the normal axis of the workpiece for performing a finishing abrading operation cycle, a gage, a first means for feeding the wheel laterally to bring about the said abrading operation, a second means for moving the wheel axially, the said second means causing the wheel to reciprocate axially within the workpiece during a portion of the cycle, means associated with the first means for terminating the said reciprocations and causing the second means to withdraw the wheel axially from the workpiece for a period of time before resuming the said reciprocations, means causing the gage to enter the workpiece during the said period to obtain a signal indicative of the size of the bore, a memory device for receiving the signal from the gage and retaining it, an actuator for continuously comparing the signal to a standard signal which standard signal increases in value as the cycle progresses, and a switch operatively connected to the actuator to terminate the cycle when the gage signal and the standard signal reach a predetermined relationship.

5. An internal grinding machine comprising means for holding a workpiece for rotation thereof, a wheel having its axis parallel to the normal axis of the workpiece for performing a finishing abrading operation cycle, a pneumatic gage, means for feeding the wheel laterally to bring about the said abrading operation, means causing the wheel to reciprocate axially within the workpiece during a portion of the cycle, means for terminating the said reciprocations and causing the wheel to be withdrawn axially from the workpiece for a period of time before resuming the said reciprocations, means causing the gage to enter the workpiece during the said period to obtain an air pressure signal indicative of the size of the bore, a reservoir for receiving the signal from the gage and retaining it, a diaphragm-type actuator for continuously comparing the signal to a standard air pressure signal which standard signal increases in value as the cycle progresses, and a switch operatively connected to the actuator to terminate the cycle when the gage signal and the standard signal reach a predetermined relationship.

6. An internal grinding machine comprising means for holding a workpiece for rotation thereof, a wheel having its axis parallel to the normal axis of the workpiece for performing a finishing abrading operations cycle, a gage, means for feeding the wheel laterally to bring about the said abrading operation, means causing the wheel to reciprocate axially within the workpiece during a portion of the cycle, means for terminating the said reciprocations and causing the wheel to be withdrawn axially from the workpiece for a period of time before resuming the said reciprocations, means causing the gage to enter the workpiece during the said period to obtain a signal indicative of the size of the bore, a memory device for receiving the signal from the gage and retaining it, means for continuously comparing the signal to a standard signal which standard signal increases in value as the cycle progresses, means terminating the cycle when the gage signal and the standard signal reach a predetermined relationship, an aftergage, and means associated with the after-gage for adjusting the standard signal to compensate for the variations in the diameters of the bores in successive workpieces.

7. An internal grinding machine comprising means for holding a workpiece for rotation thereof, a Wheel having its axis parallel to the normal axis of the workpiece for performing a finishing abrading operations cycle, a gage, means for feeding the wheel laterally to bring about the said abrading operation, means causing the wheel to reciprocate axially within the workpiece during a portion of the cycle, means for terminating the said reciprocations, means causing the gage to enter the workpiece during the said period to obtain a signal indicative of the size of the bore, a memory device for receiving the signal from the gage and retaining it, means for continuously comparing the signal to a standard signal which standard signal increases in value as the cycle progresses, means terminating the cycle when the gage signal and the standard signal reach a predetermined relationship, an after-gage, means associated with the after-gage for adjusting the standard signal to compensate for the variations in the diameters ofthe bores in successive workpieces, a truing device normally residing in an inoperative position removed from the line of movement of the wheel, and means for causing the truing device to move into an inoperative position adjacent the line of movement of the wheel at the time that the wheel is removed from the workpiece to permit the gage to enter.

8. An internal grinding machine comprising means for holding a workpiece for rotation thereof, a wheel having its axis parallel to the normal axis of the workpiece for performing a finishing abrading operation cycle, a pneumatic gage, means for feeding the wheel laterally to bring about the said abrading operation, means causing the wheel to reciprocate axially within the workpiece during a portion of the cycle, means for terminating the said reciprocations and causing the wheel to be withdrawn axially from the workpiece for a period of time before resuming the said reciprocations, means causing the gage to enter the workpiece during the said period to obtain an air pressure signal indicative of the size of the bore, a memory device for receiving the pressure signal from the gage and retaining it, means connected to a source of air to generate a standard air pressure signal which increases in value as the cycle progresses, means terminating the cycle when the gage signal and the standard signal reach a predetermined relationship, an after-gage, and a valve interposed between the means for generating the standard signal and the source of air with the after-gage for adjusting the standard signal connected by adjusting the valve to compensate for the variations in the diameters of the bores in successive workpieces.

9. An internal grinding machine comprising means for holding a workpiece for rotation thereof, a wheel having its axial parallel to the normal axis of the workpiece for performing a finishing abrading operation cycle, a pneumatic gage feed means for moving the wheel laterally to bring about the said abrading operation, means causing the wheel to reciprocate axially within the workpiece during a portion of the cycle, means for terminating the said reciprocations and causing the Wheel to be withdrawn axially from the workpiece for a period of time before resuming the said reciprocations, means causing the gage to enter the workpiece during the said period to obtain an air pressure signal indicative of the size of the bore, a memory device for receiving the pressure signal from the gage and retaining it, means associated with the said feed means and connected to a source of air to generate a standard air pressure signal which increases in value as the cycle progresses, means terminating the cycle when the gage signal and the standard signal reach a predetermined relationship, an after-gage, a valve interposed between the means for generating the standard signal and the source of-air conneced with the after-gage for adjusting the standard signal. by adjusting the valve to compensate for the variations in the diameters of the bores in successive workpieces, a truing device normally residing in an inoperative position removed from the line of movement of the wheel, and means for causing the trning device to move into an operative position adjacent the line of movement of the wheel at the time that the wheel is removed.

10. An internal grinding machine having a vworkhead for holding a workpiece and a wheelhead for holding a wheel comprising a source of air under pressure, a pneumatic gage feed means for moving the wheel laterally to bring about an abrading operation, a nozzle associated withthe said feed means andconnected to the said source of air to generate a standard air pressure signal which increases in value as the abrading operation progresses, a first means causing the wheel to reciprocate axially within the workpiece during a portion of the cycle, a second means for terminating the said reciprocations and causing the wheel to be withdrawn axially from the workpiece for a period of time before resuming the said reciprocations, a third means causing the gage to enter the Workpiece during the said period to obtain a signal indicative of the .size of the bore, a reservoir connected to the gage for receiving the signal from the gage and retaining it, a pressure switch connected to the reservoir and to the nozzle for continuously comparing the gagesignal to the standard signal, the switching terminating the abrading operation when the gage signal and the standard signal reach a predetermined relationship, an :aftergage, and means associated with the after-gage for adjusting the standard signal to compensate for the variations in the diameters of the bores in successive workpieces.

11. In an abrading machine, a work holder, a rotary abradingtool, means for applying the tool .toa workpiece in the work holder for causing an abrading operation without gaging for a predetermined .first period, means ending the first period and withdrawing the tool from the workpiece, means gaging the workpiece during the withdrawal, means causing an abrading operation'without gaging for a second period, and control means for determining the length of the second period in accordance with the gaging of the workpiece taken during the withdrawal.

References Cited in the file of this patent UNITED STATES PATENTS 2,477,508 Arms fJuly 2.6, 1949 2,585,533 Bryant et al Feb. 12, 1952 2.771.714 Schmidt et al. Nov. 27, 1956 

